1. Field
The embodiment(s) discussed herein is (are) directed to a technology for managing neighboring cell information.
2. Description of the Related Art
Mobile wireless communication, in which a plurality of cells form, in combination, a communication area, needs a process called “handover”, so that communication is not to be disconnected even when a mobile machine such as a mobile phone moves from one cell to the other. To perform handover, a base station apparatus notifies a mobile machine in its coverage cell of cells neighboring the coverage cell as neighboring cells. The mobile machine notifies the base station apparatus of the receiving state of electric wave from the neighboring cells. When there is a cell in such a receiving state that satisfies a predetermined condition, the base station apparatus determines the cell as a destination of handover.
To realize such a structure, the base station apparatus stores neighboring cell information (NCL: Neighboring Cell List) for each of cells that the apparatus accommodate. Around the cell, there may be a cell accommodated by other base station, and in such a case, a cell accommodated by other base station is included as part of neighboring cell information.
As described above, including a cell covered by another base station in neighboring cell information necessitates review of neighboring cell information of a neighboring base station apparatus when a new base station is additionally provided, or when a cell is added to an existing base station, leading the increase in number of steps of maintenance and management of neighboring cells. For example, in the case where a cell a is added in the base station apparatus A, when the cell a neighbors a cell b of a base station apparatus B, not only information of cells around the cell a should be set in the base station apparatus A as neighboring cell information, but also neighboring cell information of the base station apparatus B should be updated so that the cell a is included as neighboring cells of the cell b.
For the purpose of reducing the number of steps of maintenance and management of neighboring cell information, such a technique is proposed that a mobile exchange center (MCS) which is a higher level apparatus of the base station apparatus controls collection of information, determines the neighboring condition of cell, and instructs the base station apparatus to update neighboring cell information. Also proposed is a technique of updating neighboring cell information by exchanging information between base station apparatuses based on information sent by a mobile machine to the base station apparatus at the time of executing handover. Reference may be had to, for example, Japanese Laid-open Patent Publication Nos. H11-331931 and 2000-13843
However, the method of determining neighboring condition of cell by a higher level apparatus such as a mobile exchange center has a problem that great burden is imposed on the higher level apparatus when a cell is added in plural base station apparatuses. Further, the method of exchanging information between base station apparatuses based on information sent from a mobile machine has a problem that line is stressed as the number of mobile machines increases, and information exchanged between the base station apparatuses increases.